Among the 32 firefighters promoted to lieutenant yesterday was the son of the highest-ranking FDNY official killed on 9/11.

The newly minted lieutenant, Peter J. Ganci III, now joins his late father, Peter Ganci, and younger brother in climbing the ranks of the Fire Department.

“It is bittersweet. It is very nice. I’m very happy that I was promoted. Obviously, I miss a few aspects, namely my father,” Ganci said, after the packed promotion ceremony at La Guardia Community College attended by more than 700 firefighters, family and well-wishers.

“Obviously, I wish he was here today,” said Peter, a married father of three.

The senior Ganci was the FDNY’s chief of department — the highest-ranking uniformed officer — when he died on 9/11 directing the rescue of 25,000 people out of the burning World Trade Center towers.

He was killed when the north tower collapsed.

Peter, 38, said he believes his dad was watching from heaven.

“I sure as hell hope so. I really hope so,” he said. “I think he is.”

The elder Ganci’s legacy lives on not just in Peter, but in another firefighter son, Chris, who himself was promoted to lieutenant last year.

“I’m proud of him,” said Chris, 36, who watched his older sibling accept the promotion.

“I learned a lot from him, so I’m sure the guys out in the field will learn a lot from him, too.”

His advice to his brother on accepting the leadership role was simple: “Just take care of the men, keep them safe.”

The two brothers say they carry the weathered Mass card from their father’s funeral in their fire coats as a reminder of him. Chris also wrote a biography of their father: “Chief: The Life of Peter J. Ganci, a New York City Firefighter.”

The family got a special acknowledgment from FDNY Commissioner Sal Cassano.

“My good friend Peter Ganci made the supreme sacrifice on September 11th,” Cassano said.

“Pete’s son is getting promoted today. Peter, I know your dad would be proud of you and Chris for what you’ve done, making your own mark on this job. You are going to continue a lot of his legacy,” the commissioner said.

Bryan Cowan, Peter’s and Chris’ brother-in-law by marriage to their sister, was also promoted to lieutenant.

“My brother-in-law was promoted with me, so the whole Ganci family is celebrating today,” said Peter.